Environment Reconstruction in Terahertz Monostatic Sensing: Joint Millimeter-level Geometry Mapping and Material Identification

Terahertz (THz) integrated sensing and communication (ISAC) offers high-speed communication alongside precise environmental sensing. This paper presents a computationally efficient framework for THz-based environment reconstruction by integrating connected component analysis (CCA)-assisted multipath component (MPC) estimation with a sliding-window refinement strategy. To start with, a monostatic sensing experiment is conducted in an indoor scenario using a vector network analyzer (VNA)-based sounder operating from 290 to 310 GHz. On one hand, as for geometry mapping, a CCA-based region search is employed to accelerate parameter extraction, significantly reducing the search space for space-alternating generalized expectation-maximization (SAGE)-based estimation and achieving an 8.4 times acceleration, while preserving resolution. Further analysis of the connected component structure enables the identification of indoor features such as flat walls and corners. A sliding-window refinement applied to the identified regions improves geometric mapping, achieving the mean distance error of 4.9 mm, which is one order of magnitude better than the literature. On the other hand, the deterministic and stochastic components of the monostatic channel are classified through reflection loss analysis. Then, material identification is performed by looking up the reflection loss in a THz time-domain spectroscopy (THz-TDS) database, which comprises over 200 materials across a 0-6 THz range. Experimental results validate millimeter-level accuracy in geometry mapping and reliable material classification, enhancing the environmental awareness capabilities of THz ISAC systems.

Centimeter-level Geometry Reconstruction and Material Identification in 300 GHz Monostatic Sensing

Terahertz (THz) integrated sensing and communication (ISAC) technology is envisioned to achieve high communication performance alongside advanced sensing abilities. For various applications of ISAC, accurate environment reconstruction including geometry reconstruction and material identification is critical. This paper presents a highly precise geometry reconstruction algorithm and material identification scheme for a monostatic sensing case in a typical indoor scenario. Experiments are conducted in the frequency range from 290 GHz to 310 GHz using a vector network analyzer (VNA)-based channel sounder by co-locating the transmitter and receiver. A joint delay and angle space-alternating generalized expectation-maximization (SAGE)-based algorithm is implemented to estimate multipath component (MPC) parameters and the indoor geometry is reconstructed based on the extracted parameters. Furthermore, a geometry-based method is employed to model and remove the spurious path of the corner, reaching an accuracy of 1.75 cm. Additionally, a material database using THz time-domain spectroscopy (THz-TDS) is established, capturing reflection losses of over 200 common material samples. Applying this database to our monostatic sensing, the measured reflection losses of wall and window frame are accurately identified as cement and steel, respectively. Our results demonstrate the centimeter-level geometry reconstruction and accurate material identification for practical THz ISAC scenarios, which unleash unprecedented sensing potential compared to microwave and millimeter-wave bands.